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Casus belli

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This article is about war justifications. For the innovation, see Casus Belli (innovation).

A casus belli, the Latin for "Cause for War", (sometimes abbreviated as CB) represents a justification for war recognized as legitimate by other characters. A ruler must have a valid casus belli before declaring war upon another ruler, and can only conquer counties specified under the Objective of the casus belli.

Objective[edit]

The Objective is the map region which is targeted by a casus belli. If the casus belli does not target a map region then the defender's Realm Capital becomes the Objective.

The attacking side gains more War Score by occupying Holdings located in the Objective region and capturing Important Prisoners. After a grace period, the defender will passively gain War Score if they holding all Counties in the Objective region.

Casus belli list[edit]

Each casus belli will cost Prestige and/or Piety. If a character cannot pay the cost, then they can pay with a Level of Fame or Level of Devotion instead. Declaring war against a character's head of faith costs 500 Piety if the Head of Faith is Spiritual and 100 Piety if the Head of Faith is Temporal.

Note that:

  • Prestige De Jure claims require Innovations.
  • Characters' Claims may not be valid casus belli, depending on the Faith's View on Gender.
    • For Faiths with Male Dominated doctrine, female characters' Claims may not be used to seize titles from male titleholders, unless the targeted ruler is a child or  Incapable.
    • For Faiths with Female Dominated doctrine, male characters' Claims may not be used to seize titles from female titleholders, unless the targeted ruler is a child or  Incapable.

Casus belli costs can be removed via one of the game rules.

General CBs[edit]

Casus belli Requirements Cost War outcome victory.png Enforce Demands effect War outcome white peace.png White Peace effect War outcome defeat.png Surrender effect
Independence War Target is the liege
  • 500 Prestige if not tribal
  • 250 Prestige if tribal
Attacker becomes independent Attacker stays a vassal
Seize De Jure County
  •  Casus Belli innovation (Tribal era)
  • De jure cb.png De jure title above target county
100 prestige
  • The de jure liege in attacker's realm gains the targeted county
  • If that character is not attacker, attacker gets a weak hook (Favor) on them
Defender keeps their titles
  • Defender keeps their titles
  • Attacker pays war reparations
Seize De Jure Duchy
  •  Chronicle Writing innovation (Early Medieval era)
  • De jure cb.png De jure title above target duchy
100 prestige per county
  • The de jure liege in attacker's realm gains the targeted county
  • If that character is not attacker, attacker gets a weak hook (Favor) on them
Defender keeps their titles
  • Defender keeps their titles
  • Attacker pays war reparations
Seize De Jure Titles
  •  Rightful Ownership innovation (Late Medieval era)
  • De jure cb.png De jure titles above targets
100 prestige per county
  • All titles that are de jure vassals of characters in attacker's realm are gained by those characters
  • Attacker gets a weak hook (Favor) on each vassal who gains a title this way
Defender keeps their titles
  • Defender keeps their titles
  • Attacker pays war reparations
Claims
  • Claim on the target
  • Pressing several of one's own claims at once requires the  Divine Right innovation (High Medieval era)
  • Pressing several of another's claims at once requires the  Rightful Ownership innovation (Late Medieval era)
  • 100 prestige per county (own claim)
  • 200 prestige per duchy (own claim)
  • 400 prestige per kingdom (own claim)
  • 800 prestige per empire (own claim)
  • 250 prestige per county (other's claim)
  • 500 prestige per duchy (other's claim)
  • 1000 prestige per kingdom (other's claim)
  • 3000 prestige per empire (other's claim)
  • 125 prestige if claimant is of different dynasty
  • Claimant gains the targeted titles
  • Attacker gets a weak hook (Favor) on any other character who gained titles
Defender keeps their titles
  • Defender keeps their titles
  • Claimant loses the claims used
Subjugate Yes One of the following:
  • 1000 prestige if not tribal
  • 500 prestige if tribal
Attacker vassalizes the defender Defender stays independent
Raid for Captives Core tenet flagellant.png Faith has the Human Sacrifice tenet
  • 80 if faith has the Armed Pilgrimages tenet
  • 100 otherwise
  • If both attacker and defender follow the same faith, they will both receive regardless of the outcome (less for the loser)
Attacker imprisons 3–5 of the defender's courtiers Attacker gains no prisoners
  • Attacker gains no prisoners
  • If defender also follows a faith that has the Human Sacrifice tenet, defender imprisons 3-5 of the attacker's courtiers
Excommunication War
  • Yes Same faith as defender and any liege(s), and that faith allows excommunication
  • Yes Target is independent
  • Target has the Excommunicated trait
None Defender is deposed (i.e. succession happens as though the character had died) Defender keeps their titles
  • Defender keeps their titles
  • Defender loses the Excommunicated trait
  • Attacker loses Opinion with head of faith
Ducal Conquest of County
  • Diplomacy lifestyle.png Ducal Conquest lifestyle perk (Diplomat tree)
  • Attacker owns a county in the same uncreated duchy as the target county
  • 350 prestige if target's title rank is count
  • 750 prestige if target's title rank is higher than count
Attacker gains the target county Defender keeps their titles
  • Defender keeps their titles
  • Attacker's factions gain discontent
Forced Vassalization
  • Diplomacy lifestyle.png Forced Vassalage lifestyle perk (Diplomat tree)
  • Yes Defender is an independent neighbouring realm with no more than 3 counties, plus 2 for each of the following innovations:
    •  Casus Belli (Tribal era)
    •  Chronicle Writing (Early Medieval era)
    •  Divine Right (High Medieval era)
    •  Rightful Ownership (Late Medieval era)
  • No Defender is not a holy order or attacker's head of faith
125 prestige per county Attacker vassalizes the defender Defender stays independent
  • Defender stays independent
  • Attacker's factions gain discontent
Laudably Conquer County
  • Request Claim on Ireland decision
  • Attacker and defender don't have the same top liege
  • Target county is in the Hibernia region
  • 150 prestige if feudal and different faith
  • 75 prestige if tribal and different faith
  • 100 piety if feudal and same faith
  • 50 piety if tribal and same faith
Attacker gains the defender's titles Defender keeps their titles
  • Defender keeps their titles
  • Attacker's factions gain discontent
Mongol Invasion of Empire
  • Mongol Empire title
  • Yes Tribal government
  • Fame level is Established or higher
  • Target title is adjacent to attacker's realm
200 prestige Attacker vassalizes all rulers in target empire within defender's realm whose religion is more tolerated by attacker than defender's, and gains all other counties Defender keeps their titles
  • Defender keeps their titles
  • Attacker's factions gain discontent
Restore Imperial Province
  • Roman Empire title
  • De jure cb.png Duchy was part of the Roman Empire
  • Yes Religion is Christian or Greco-Roman
None Attacker gains all land in the target duchy within defender's realm Defender keeps their titles
  • Defender keeps their titles
  • Attacker must pay war reparations

Conquest CBs[edit]

The following CBs are only available to rulers who either have clan or tribal government, an unreformed faith, or their faith has the Warmonger or Pursuit of Power tenets.

  • If the war ends by enforcing demands, the attacker will gain the target title and fame equal to the war contribution share.
  • If the war ends by white peace, the defender keeps the target title and the attacker loses 75  prestige.
  • If the war ends by surrender, the defender's keeps the target title and the attacker must pay  gold and gain +25 faction discontent.
Objective rank Required level of fame Same faith cost Different faith cost War contribution share Once per lifetime
 County Established
  • 50 if character has tribal government
  • 100 if character has clan government
  • 75 if character has tribal government
  • 150 if character has clan government
75 No
 Duchy Icon prestige 03.png Illustrious
  • 250 if character has tribal government
  • 500 if character has clan government
  • 375 if character has tribal government
  • 750 if character has clan government
150 No
 Kingdom Icon prestige 04.png Exalted among Men 2000 2000 350 Yes

Holy War CBs[edit]

The following CBs will cause a holy war instead of a regular one. They require the faith to be organized and to not have the Pacifism or Dharmic Pacifism tenets, and can only target rulers whose faith is considered hostile or evil.

  • If the war ends by enforcing demands, the attacker will gain all titles held by rulers of different faith and vassalize all rulers of the same faith in the target region.
  • If the war ends by white peace, then the defender keeps all their titles and the attacker loses 50 piety.
  • If the war ends by surrender, then the defender keeps all their titles, its faith gains fervor equal to the attacker's cost, and the attacker must pay  gold and gain +25 faction discontent and −15 vassal opinion for 5 years.
Objective rank Required level of devotion  Fervor cost  Piety cost (without Armed Pilgrimages tenet)  Piety cost (with Armed Pilgrimages tenet) War contribution share Once per lifetime
 County Dutiful 1 100 80 100 No
 Duchy Faithful 2 200 160 200 No
 Kingdom Paragon of Virtue 5 750 600 500 Yes

Migrate to Pannonia[edit]

Migrate to Pannonia is a unique casus belli with special mechanics that can only be used once per game by characters of Táltosist faith who make the Prepare to Cross the Carpathians decision against characters in the Pannonian Basin region. If the Hungarian Migration game rule is set to Immediate the game will start with the casus belli being used by Grand Prince Álmos Ügyekfi of the Mogyër Confederation against King Boris of Bulgaria.

If the war ends in white peace, the defender keeps his or her titles. If it ends in surrender, the attacker's factions will also gain discontent. If the war ends by enforcing demands however it will have the following effects:

  • Attacker gains all titles held by the defender in the Pannonian Basin region
  • Attacker gains the Grand Principality of Pannonia title, and any Principality titles with de jure capitals in the captured territory.
  • Any other kingdom title held by the attacker is destroyed
  • Any held title that is not within the de jure realm of Grand Principality of Pannonia is given to another character
  • All vassals that are not within the de jure realm of Grand Principality of Pannonia become independent
  • All controlled counties convert to Mogyër culture and Táltosist faith
  • All previously controlled counties convert to Pecheneg culture

When the casus belli is used it will spawn the following army for as long as the attacking character lives:

Years Levies Unit horse archers.png Horse Archers
867-889 3000 2000
890-904 5000 3000
905-910 6000 4000
Characters CharactersAttributesTraitsResourcesLifestyleDynastyCultureInnovationsModifiers
Realm & Governance VassalsCouncilCourtSchemesGovernmentLawsDecisionsTitlesBaronyCounty
Warfare WarfareCasus belliAllianceArmyHired forces
Faith ReligionFaithDoctrinesTenets
Meta ModdingPatchesDownloadable contentDeveloper diariesAchievementsJargon